C OMPUTING E SSENTIALS Presentations by: Fred Bounds Timothy J. O’Leary Linda I. O’Leary

6 6 Communications and Connectivity CHAPTER

3 Computing Essentials Chapter 6 Competencies After reading this chapter, you should be able to: 1. Describe connectivity options: fax machines, , voice-messaging systems, videoconferencing systems, shared resources and online services. 2. Describe conventional modems, T1, ISDN, ADL and cable modem connections.

4 Computing Essentials Chapter 6 Competencies 3. Describe the cable and air communications channels - telephone, coaxial, fiber-optic, microwave and satellite. 4. Discuss bandwidth, serial versus parallel transmission, direction and modes of data transmission and protocols.

5 Computing Essentials Chapter 6 Competencies 5. Explain network architecture - configurations and strategies. 6. Describe local area, metropolitan area and wide area networks.

6 Computing Essentials Chapter 6 Overview Connectivity is the microcomputer’s capability to access information from beyond the desktop Taken for granted today, it is particularly important in business Electronic systems transmitting data from one place to another over various channels are called data communication systems

Communications and Connectivity With communications capability, microcomputer users can transmit and receive data and gain access to electronic information resources.

8 Computing Essentials Chapter 6 Scan the image of a document Convert the image to signals for transmission over phone lines Fax Machines

9 Computing Essentials Chapter 6 Transmit the signals over phone lines Receive the signals and convert them to printed output Fax Machines

10 Computing Essentials Chapter 6 Also known as electronic mail Electronic messages between individuals using a computer Messages written just like a traditional letter, except that its transmitted electronically to some individual or company’s mail box

11 Computing Essentials Chapter 6 User name and password required for use - thus affording some confidentiality Memos can be broadcast to numerous recipients at one time A powerful communications tool In wide use today

12 Computing Essentials Chapter 6 Microsoft Outlook Express client

13 Computing Essentials Chapter 6 Voice-Messaging Systems Computer systems linked to telephones that convert the human voice into digital bits More capabilities than simple answering machines and electronic mail Can receive and properly route large numbers of calls, deliver same message to multiple recipients, forward to other locations

14 Computing Essentials Chapter 6 Videoconferencing Systems Allow geographically separated individuals or groups to have in-person meetings

15 Computing Essentials Chapter 6 Videoconferencing Systems Inexpensive desktop versions are stimulating wider usage

16 Computing Essentials Chapter 6 Shared Resources Connectivity allows the cost effective sharing of expensive resources such as laser printers, disk packs, or magnetic tape storage Connectivity also gives users the ability to share data

17 Computing Essentials Chapter 6 Shared Resources Downloading means transferring data from a larger computer system to your microcomputer Uploading means transferring data from your microcomputer to a larger computer system

18 Computing Essentials Chapter 6 Online Services Businesses that offer microcomputer users connections to computer systems that offer a wide variety of information and capabilities such as –Teleshopping –Home banking –Investing –Travel reservations –Internet access

19 Computing Essentials Chapter 6 America Online

User Connection Conventional modems convert analog and digital signals. Other user connections are T1, ISDN, ADSL cable modems.

21 Computing Essentials Chapter 6 User Connection A primary means of connecting computer users is over telephone lines. General purpose phone lines transmit analog signals, whereas computers generate digital signals.

22 Computing Essentials Chapter 6 Modems Modems translate digital signals from a computer into analog signals for phone line transmission Modems translate analog signals from a phone line back to digital for processing by a receiving computer Most common and best understood measurement of speed is bits per second (bps)

23 Computing Essentials Chapter 6 Types of Modems External - connects to the serial port and to a telephone jack

24 Computing Essentials Chapter 6 Types of Modems Internal - plugged into an expansion slot on the motherboard

25 Computing Essentials Chapter 6 Types of Modems Wireless - connects to the serial port like an external modem, but receives transmissions through the air, like a cell phone.

26 Computing Essentials Chapter 6 Other Connections Leased, special high-speed phone lines include: T1, T2, T3 and T4, and support high capacity digital communications ISDN - uses high-speed lines to achieve twice the speed of conventional modems

27 Computing Essentials Chapter 6 Other Connections ASDL (asymmetric digital subscriber line) - uses existing phone lines to match T1 speeds Cable modems - existing television cable networks to match T1 speeds

Communications Channels Data may flow through five kinds of communications channels: telephone lines, coaxial cable, fiber-optic cable, microwave and satellite.

29 Computing Essentials Chapter 6 Telephone Lines Consists of twisted pairs of copper wires The basic communication channel for the phone system for almost one hundred years Cheap and readily available Being phased out in favor of other media

30 Computing Essentials Chapter 6 Coaxial Cable High frequency transmission Single solid copper core 80 times the capacity of twisted pair

31 Computing Essentials Chapter 6 Fiber-Optic Cable Pulses of light, rather than electrons, represent data 26,000 time the transmission capacity of twisted pair Immune to electronic interference

32 Computing Essentials Chapter 6 Microwave High-frequency radio waves Travels in straight lines through the air Short distances between devices, wave can’t bend with curvature of the earth

33 Computing Essentials Chapter 6 Satellites Typical orbit is 22,000 miles above the earth Also function as microwave relay stations Can be used to send large volumes of data Can transmit long distances due to height above the earth’s surface

34 Computing Essentials Chapter 6 Satellites Typical orbit is 22,000 miles above the earth Also function as microwave relay stations Can be used to send large volumes of data Can transmit long distances due to height above the earth’s surface

Data Transmission Several technical matters affect data communications. They are bandwidth, serial versus parallel transmission, direction of flow, modes of transmission and protocols.

36 Computing Essentials Chapter 6 Bandwidth The bits-per-second transmission capability of a channel

37 Computing Essentials Chapter 6 Bandwidth Three different types –Voiceband - standard phone line, used with microcomputers, typical speeds from 9,600 to 28,800 bps –Medium band - with special leased lines for larger computer systems; speeds from 56k to 2.6 million bits per second –Broadband - includes microwave, satellite, coaxial cable and fibre-optic channels; speed range from 56 k to 30 million bps

38 Computing Essentials Chapter 6 fibre-optic - 26,000 coaxial - 80 twisted-pair - 1 Bandwidth - Number of Connections

39 Computing Essentials Chapter 6 Serial and Parallel Transmission Serial - continuous stream of bits, one at a time, like a one lane road; most common form over phone lines Parallel - bits simultaneously flowing in separate but parallel wires; like an eight land highway; most common connection to the printer

40 Computing Essentials Chapter 6 Serial versus parallel transmission

41 Computing Essentials Chapter 6 Direction of Data Transmission Simplex - data travels in one direction only, like a one-way street Half-duplex - data flows both ways, but not simultaneously; like traffic on a one- lane bridge Full-duplex - two-way transmission, at the the same time; like traffic on a two- way street

42 Computing Essentials Chapter 6 simplex half-duplex Full-duplex Direction of Data Transmission

43 Computing Essentials Chapter 6 Modes of Transmitting Data Asynchronous transmission - data is sent and received one byte at a time; drawback is transmission time Synchronous transmission - for larger loads, several bytes or a block at a time; sending and receiving coordinated by a synchronized clock

44 Computing Essentials Chapter 6 synchronous versus asynchronous transmission

45 Computing Essentials Chapter 6 Protocols A set of communication rules for the exchange of information As protocols become more complex, the need for standards increases

Network Architecture Network architecture describes how a computer network is configured and what strategies are used.

47 Computing Essentials Chapter 6 Network Architecture Networks are connections of two or more computers that work together to exchange information and share resources The network architecture describes how the network is arranged and how the resources are coordinated and shared

48 Computing Essentials Chapter 6 Network Architecture Terms Node - any device connected to a network Client - a node that requests and uses resources available from other nodes Server - a node that shares resources with other nodes

49 Computing Essentials Chapter 6 Network Architecture Terms Network operating system (NOS) - software to control and coordinate activities between computers on a network Distributed processing - computing power located and shared at different locations Host computer - large centralized computer, usually a mainframe

50 Computing Essentials Chapter 6 Configurations Network arrangement or configuration called a topology Star - nodes are connected to a single computer –All communications pass through this host –Can be used as a time sharing system

51 Computing Essentials Chapter 6 Star network

52 Computing Essentials Chapter 6 Configurations Bus network - each device handles its own communications control –No host computer –Common connecting cable called a bus –Not as efficient as star, but it is low cost and widely used

53 Computing Essentials Chapter 6 Bus network

54 Computing Essentials Chapter 6 Configurations Ring network - each device connected to two other devices, forming a ring –No central computer –Useful as a distributed data processing system Hierarchical network - combinations that feature both centralized and decentralized designs

55 Computing Essentials Chapter 6 Ring network

56 Computing Essentials Chapter 6 Hierarchical network

57 Computing Essentials Chapter 6 Strategies Ways of coordinating the sharing of information and resources in a network Terminal network system –Centralized host, usually a mainframe –Nodes are usually terminals with little or no processing capabilities –Reservation systems

58 Computing Essentials Chapter 6 Strategies Peer-to-peer network system - nodes act as both servers and clients –A node could obtain files from another node, and provide files to another node –Bus topology best example

59 Computing Essentials Chapter 6 Strategies Client/server network systems –Powerful computer coordinates services –This server provides access to centralized resources Enterprise computing describes the trend toward integrating or connecting all of company’s computer resources together

Network Types Communications networks differ in geographical size. Three important types are LANs, MANs and WANs.

61 Computing Essentials Chapter 6 Local Area Networks Computers and devices are linked in close proximity to each other Often called LAN’s Linked by cable Typically use a bus form of organization With gateways, LAN’s can be connected to other LAN’s or any other type of network

62 Computing Essentials Chapter 6 A LAN with a file server and network gateway

63 Computing Essentials Chapter 6 Metropolitan Area Networks Network linking nodes and resources within the geographical bounds of a city Cellular phones can extend the reach of a MAN

64 Computing Essentials Chapter 6 Wide area network

65 Computing Essentials Chapter 6